A Simple Breath Test That Can Help Clarify Your Asthma Care

Asthma can feel unpredictable. Some days breathing feels normal, while other days symptoms such as cough, chest tightness, or shortness of breath can appear without warning. One reason asthma can be hard to manage is that symptoms do not always reflect what is happening inside the airways.

A test called FeNO (fractional exhaled nitric oxide) can help provide additional clarity.

What Is FeNO Testing?

FeNO is a simple, non-invasive breathing test that measures a natural gas in your breath called nitric oxide. Higher levels of nitric oxide are often linked to a specific type of airway inflammation that is common in many people with asthma.

The test involves breathing slowly into a handheld device for a few seconds. It is painless, does not require needles, and provides results immediately.

Why Might My Doctor Recommend FeNO?

FeNO testing can help your healthcare provider:

• Understand whether airway inflammation is contributing to your symptoms

• Determine whether inhaled anti-inflammatory medications (such as corticosteroid inhalers) are likely to help

• Assess whether current asthma treatment is working as expected

• Avoid unnecessary medication changes when inflammation is not present

This is especially helpful if you:

• Have ongoing symptoms despite normal breathing tests

• Have chronic cough or unclear asthma symptoms

• Are unsure whether your inhaler is helping

• Want a more personalized approach to asthma care

How FeNO Fits With Other Lung Tests

At One Breath, FeNO testing is used alongside pulmonary function testing, not instead of it.

• Spirometry measures how well air moves in and out of your lungs

• Lung volume testing shows how much air your lungs can hold

• Diffusion capacity testing evaluates how well oxygen moves into your bloodstream

• FeNO testing adds information about airway inflammation

Together, these tests provide a more complete picture of lung health than any single test alone.

What the Test Can—and Cannot—Tell Us

FeNO testing can be very informative, but it is not a diagnosis by itself. A high or low result must always be interpreted in the context of your symptoms, medical history, and other test results. Your referring clinician will review the results and decide how they fit into your overall care plan.